Thursday, February 16, 2017

Seneca Falls "Star" 10-inch lathe - cross slide chip guard

I have an old lathe in the basement, keeping the sewing machines company. The lathe is a little over 100 years old. How do I know that, you ask? It has several patent dates cast into the bed and the most recent is 1910 (the oldest is 1895). If it were made in 1916 or after, it would have a 1916 patent date also.

Recently I did get a new-to-me toy in the garage too. A Smithy lathe/mill:

So what better way to break in the new lathe than to whittle a chip guard for the Star lathe. I inherited this Star lathe from my late father-in-law and unbeknownst to me, ever since I've had it, it has been missing a chip guard on the cross slide. The photo below shows the new guard in place.

Just a couple weeks ago I was fiddling with the old Star lathe and made the startling realization that there should be a chip guard over the cross slide screw threads. A hole that I had previously assumed was an oil hole was indeed a threaded hole. The puzzle pieces were beginning to fall into place. Below is a photo of the hole (and the screw I had to make). The hole threads were .190-28 (#10-28), a very oddball size. Standard #10 screws are 10-24 and 10-32, and I had taps and dies for only those two sizes. But not to fear, I have machines that can solve problems like this.

Here is the completed screw that I made on the Harbor Freight mini lathe (yes, I have three lathes):

Next I bought a piece of 1/4" x 4" aluminum to make the chip guard from. It needed to be about 3-1/8" wide, so I couldn't use 3" wide aluminum. Well, I could, but it wouldn't look as nice if it didn't cover the entire width of the cross slide. Below I am cutting almost an inch from the width:

After the rough band saw cut, I milled the edges to get the correct width (the mill has an inexpensive DRO that is basically an electronic caliper affixed to the quill):

As seen in photo of the screw three photos up, the guard needs to have a .305"-wide and .063" tall protrusion that fits into the groove seen in the cross slide. This calls for some milling. I used the Smithy mill with a 1/2" diameter 2-flute end mill. I used some 3/4" gage blocks (see below) in the vise to support the aluminum. I did also find out that the vise has a capacity of about 3.08 inches, so by default my part had to be that width, and not 3.125 as I had originally planned (sigh).

I used a .006 lead screw feed rate (levers set at 6 and II). The first pass I tried at .012 but it seemed too fast.

Below shows the first mill pass (I didn't have gage blocks precisely the right height to be able to position the aluminum above the top of the vise jaws so I had to cantilever the part off the side of the vise; not ideal but it worked):

Below is the finished part, other than to drill the screw hole and finish the edges with a file.

Here is the guard, installed in all it's glory (I rounded the end away from the tool post to make it look a little more finished):

... and another photo of the lathe with the guard:

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